Abstract
Hydrogen peroxide (H(2)O(2)) in plants is produced in relatively large amounts and plays a universal role in plant defense and physiological responses, including the regulation of growth and development. In the Rhizobium-legume symbiosis, hydrogen peroxide plays an important signaling role throughout the development of this interaction. In the functioning nodule, H(2)O(2) has been shown to be involved in bacterial differentiation into the symbiotic form and in nodule senescence. In this study, the pattern of H(2)O(2) accumulation in pea (Pisum sativum L.) wild-type and mutant nodules blocked at different stages of the infection process was analyzed using a cytochemical reaction with cerium chloride. The observed dynamics of H(2)O(2) deposition in the infection thread walls indicated that the distribution of H(2)O(2) was apparently related to the stiffness of the infection thread wall. The dynamics of H(2)O(2) accumulation was traced, and its patterns in different nodule zones were determined in order to investigate the relationship of H(2)O(2) localization and distribution with the stages of symbiotic nodule development in P. sativum. The patterns of H(2)O(2) localization in different zones of the indeterminate nodule have been partially confirmed by comparative analysis on mutant genotypes.